Shape hopper

In order to apply Fick s Lrst law to the low of particulate material, we refer again to the above case study, that is, the discharge of the particulate material out of a conical-shaped hopper with an oriLce of 5 mm and a half-center angle of fee Figure 20.17). 

The relation between mass and funnel flows for conical bins is shown in Fig. 21-20. The angle of kinematic friction which is a measure of the friction coefficient between the solid and the material of construction used for the conical-shaped hopper, is measured with the flow-factor tester. The degree of finish of the metal surface can have a large effect in determining whether the vessel will function in mass or funnel flow. Finer degrees of finish are being used more fre-... 

Screw feeders used to discharge from bulk storage are normally designed as an integral feature of the facility, see Fig. 2.12. Their essential function is to provide a reliable discharge of the stored contents. The favourable flow form offered by wedge-shaped hoppers, facilitated by a slot outlet, is often a main reason for using a screw feeder. A second common objective... 

Equation 7.29 generally overestimates the flow rate by about 40 to 100%, as determined by comparison to experimental results. Savage [30] extended his analysis to include the effect of wall friction by solving the equations of motion by the method of integral relations. The flow rates were lower than predicted with Eq. 7.29, but still higher than experimental values. Savage and Sayed [31] improved the earlier analysis [30] and derived an expression for the flow rate in a two-dimensional wedge-shaped hopper ... 

The hopper flow factor, //, is a function of b, w/ and 6 and can be calculated from first principles. However, Jenike (1964) obtained values for a conical hopper and for a wedge-shaped hopper with a slot outlet for values of b of 30°, 40°, 50°, 60° and 70°. Examples of the flow factor charts for conical hoppers are shown in... 

For a wedge-shaped hopper, the outlet length must be at least two times its width if the end walls are vertical and at least three times its width if the end walls are converging. 

Jones M.G., Marjanovic P, McGlinchey D. Investigation Of The Discharge Pattern Of Industrial Coals From Wedge Shaped Hoppers, Proc of Int Symp Reliable Flow of Particulate Solids III (Relpowflo III), Porsgrunn, Norway, pp546-552,1999. 

FIGURE 8.10 Cylindiically shaped hopper partially filled with granular solids. The nonisotropic pressure distribution is described by the parameter K. 

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